Jiji-ji-gi: Sascoronavirus-2’s ‘Achilles tendon’

What is the identity of Sascoronavirus-2, which has driven the world into fear and panic? To end corona19 pandemic with human ity, we must first know the enemy we are facing.

The virus is a nucleic acid surrounded by protein. Depending on the type of nucleic acid is divided into ‘DNA virus’ and ‘RNA virus’, among them RNA viruses are unusually troublesome evils. Coronavirus is also a type of RNA virus that uses RNA as a dielectric. RNA virus frequently causes mutations in the proliferation process. The drug resistance is handsome, and vaccines are often obsolete. In addition, it is able to change the host through mutations, so even the virus of the animal can cross the interspecies barrier to humans.

In addition to the corona-based virus, there are many notorious RNA viruses. Typical examples include the influenza virus, which kills tens of millions of people at the beginning of the 20th century and is still prevalent, the AIDS-causing virus that causes nearly one million deaths each year, the human immunodeficiency virus (HIV), the Ebola virus with a processing mortality rate of more than 50%, and the Zika virus that has disrupted the Brazilian Olympics. Usually RNA is known as an unstable substance. But how could these substances spread around the world in a matter of months?

The Basic Scientific Research Institute (IBS) RNA research team led by my team completed a high-resolution genetic map by analyzing the genome and transcripts of the virus that proliferated in host (monkey) cells to properly determine the identity of sascoronavirus-2, and recently published a paper in the international journal Cell (Kim et al., 2020). The Architecture of SARS-CoV-2 Transcriptome). Based on this finding, the Corona 19 Scientific Report will cover how rna, the genome of sascoronavirus-2, is replicated and amplified, and what genetic information it contains. We would like to discuss what strategies should be taken to develop a therapeutic agent.

Virus Designer, Genomic RNA (gRNA)

The size of the sarscoronavirus-2 particles is about 0.1 ° (micrometer ≤ 1m is 1m of a million th) in the shell made of lipid film and protein contains a strand of RNA called gRNA (genomic RNA ≤ genomic RNA). RNA is a polymer of nucleotides with four types of bases (A, U, G, C), such as DNA. Depending on which base is listed in what order, it will contain different information. Just as morse code contains meaning in two types of code, RNA is to encrypt the genetic information with four types of bases.

GRNA of sarscoronavirus-2 is a line of approximately 30,000 bases. Considering that the base of the human RNA is an average of 3000, the RNA of HIV is made up of about 10,000 bases, the gRNA of sascoronavirus-2 is a large RNA so that it is unique.

The virus can enter the cell after the determination with the receptor ACE2 of the cell surface using a spike protein (S protein) of the particle surface. Once the penetration is successful, the lipid membranes and proteins that form the shell of the virus fall off, the gRNA released from the protein shell is very busy from this time on.

The first thing gRNA does is to produce enzymes that will replicate itself (Sola et al., 2015, Ann. Rev. Virol). For enzyme production, ribosomes, a protein production plant in host cells, are utilized. There is a long gene called ORF1 in the anterior two-thirds of the virus gRNA. The incredibly long proteins that this gene makes have an enzyme function that cuts proteins (called proteases or protein scissors) and cuts themselves into 16 pieces.

RNA polymerase produced after sarscoronavirus-2 invades the cell plays a key role in the growth of the virus. On the other hand, by transcribing a large amount of the genomic RNA (gRNA) of the virus, the sub-dielectric RNA (sgRNA) to create a viral structure. Available for IBS

Virus Replication Workers, Unstructured Protein (NSP)

These protein fragments, called ‘nsp and nonstructural proteins’, lead viral replication in host cells. Unstructured proteins must be divided into 16 pieces, like lego blocks, to perform each mission. Therefore, inhibiting the division process limits virus proliferation. For example, caletra (a mixture of lopinavir and ritonavir) was developed as an inhibitor for protein cutting enzymes of HIV. Caletra is a candidate for the Sascoronanovirus-2 drug, but so far, reports have not been easy to expect. Research for the development of therapeutic agents specialized in protein cutting enzymes of sarconovirus-2 continues. Recently, German researchers used X-ray crystallography to reveal the structure of the protease (Mpro) of the virus and presented a drug candidate to inhibit the enzyme (Zhang et al., 2020, Science).

One of the non-structural proteins, nsp12, is rna polymerase (RdRP · RNA-dependent RNA Polymerase) has a function (Snijder et al., Advances in Virus Research, 2016). RNA polymerase can be referred to as a replication machine. Replication of rna of the virus in large quantities and produces transcripts (mediated substances utilized when genes produce proteins). RNA polymerase uses a single strand of gRNA as a casting to create the opposite strand. In order to distinguish the RNA strands, the gRNA is called a positive strand (positive-sense RNA), the opposite side of the negative strand (negative-sense RNA). Voice strand RNA is again a casting is used to mass-produce positive strands. Through this process, tens of thousands of offspring gRNA is made even if only one gRNA enters the cell.

Therefore, if inhibiting rna polymerase can effectively prevent the proliferation of viruses. There are many therapeutic candidates currently being clinically used in this treatment strategy. Remdesivir (remdesivir) was developed as an Ebola virus RNA polymerase inhibitor, avigan (Avigan, component name Favipiravir) inhibits type A influenza RNA polymerase. In vitro, agan has been revealed that the efficacy of inhibiting sascoronaoro virus-2, yet clinical therapeutic effect has not been verified.

virus mutations, adverse or advantageous, or

Mistakes also occur while RNA synthesis takes place. Sascoronaorvirus-2 is equipped with a device to avoid this because it can cause problems with virus growth when the mutation occurs due to the malfunction of the RNA polymerase nsp12. RNA-degrading enzyme nsp14 acts as an eraser to correct by cutting the wrong base. Mutations occur occasionally because they cannot always be perfect. Our research team (IBS RNA Research Group) has identified in recent studies that rna polymerase of sascoronavirus-2 is also removed part of the gene in the process of discontinuous RNA synthesis.

These mutations mostly work adversely to the survival of the virus. In rare cases, however, rather than increase the infectious ness or to be able to cross the inter-species barrier (e.g., from the heavens to humans) to increase the viability and propagation of the virus. However, experts believe that mutations that appear during short-term fashion are extremely unlikely to create a more propagation-resistant variant virus. There is also the hypothesis that the recent sascoronavirus-2 variants in Europe have a higher mortality rate, but it seems that there is no need to worry too much because it is not a claim based on sufficient analysis.

However, even if the vaccine or therapeutic agent is developed because of the mutation of the virus, the effect is less than expected. In addition, it is necessary to continuously monitor and respond because the emergence of new variants of the virus may occur over a long period of several years or more.

Sub-dielectric RNA (sgRNA) to complete the exterior, structure of replication virus

So far, we’ve seen replication of gRNA. In fact, gRNA alone is almost not infectious. It is necessary to have ‘structural proteins’ that package gRNA and ‘accessory proteins’ that act as auxiliary. To produce these proteins, the virus makes several small sub-dielectric RNA (subgenomic RNA ≤ sgRNA). Transcripts produced by RNA polymerase produces the sub-dielectric RNA.

Sascoronavirus-2 is the ORF1a gene makes a long protein chain, the protein chain is divided into several non-structured proteins (NSP) and the proliferation of the virus begins (above). Below, the IBS RNA research team with sub-dielectric RNA (sgRNA) to create components and structures of sascoronavirus-2 has identified that at least nine types of sgRNA are made. Available for IBS

Our research team analyzed the nucleotide sequence of RNA to find all the RNA produced in the host cell new coronavirus-2, and found that at least nine kinds of sgRNA is made (Kim et al., 2020). It was previously known that there were 10 types of sgRNA, but only nine of them were confirmed to actually exist. Structural protein new clio capsseed protein (N), spike protein (S), membrane protein (M), sgRNA and accessory protein (ORF3a, ORF6, ORF7a, ORF7b, ORF78) to create the sgRNA to create the outer protein (E) corresponds to this.

N sgRNA can also make a protein called ORF9b in addition to the N protein. A treatment strategy to interfere with the process of entering the virus cells made of a double spike protein as a water-soluble recombinant protein has also been recently proposed. Spike proteins as well as other viral proteins can potentially be a target of therapeutics. The table below summarizes the function of the virus protein. Since the study of sarscoronavirus-2 is still incomplete, it is estimated based on research on other existing coronavirus.

The function of the sascoronavirus-2 proteins that have been revealed so far. Available for IBS

In addition to the nine sgRNA, the study also found dozens of new sgRNA species that were previously unknown, and that some RNA had unusual chemical markers (deformations). We don’t yet know what the new saspanorvirus-2 features mean, but we can guess that they are essential to the life of the virus. Used for viral RNA replication, or seems to function to avoid the immune action of host cells. We hope that further research will help us find the hidden weaknesses of the virus.

Corona19 requires steady basic research to end

Coronavirus, which was thought and ignored only as a cold byros, is already causing the third most deadly infectious disease with coronavirus infection-19 (COVID-19) followed by SARS (SARS) in 2002 and MERS in 2014. Furthermore, it is highly likely that this trend will not be the last. Given the characteristics of mutations that occur quickly and move the host well, another new coronavirus may emerge within a few years.

Of course, human defense skills are not worth it. Many scientists around the world are running to develop treatments and vaccines. However, impatient expectations should be left. Developing effective and safe treatments and vaccines can usually take years. Humanity has yet to know much about the new coronavirus. He’s fighting an enemy he doesn’t know. To win this fight, humanity must properly grasp the characteristics of the enemy and find a way to attack the Achilles tendon. This is why we should focus on the basic research on coronavirus, even though it is too late.

Epilog

The news of the new coronavirus, which was reported in January, was not unusual. In February, the number of domestic patients began to increase, and the infection and mortality rate in Wuhan was judged to be not an easy situation to pass. The IBS RNA Research Group has the world’s best RNA research capabilities and has been conducting various viral studies. In particular, since Professor Jang Hye-sik, a member of the research team, introduced and developed a technique for analyzing the nucleotide sequence sequencing of RNA many years ago, it is already ready to analyze the coronavirus RNA genome.

There was a consensus within the research team that our research team should help society through what it could do well. While working to obtain a sample of the virus, Jung-hye No, chairman of the Research Foundation, and Jung Eun-kyung, director of the Centers for Disease Control, helped. When the experiment started to take samples at the end of February, there was already an explosion in cod patients. It was an imminent situation in which all experiments had to be conducted without making any mistakes. The first experiment began friday evening at 7 p.m. I helped with the experiment by watching researcher Kim Dong-wan (the first author) extract the virus RNA with a tense expression. After that, all the team members forgot the weekend and worked on experimentation and analysis, allowing them to submit their papers in mid-March. Cell also quickly completed peer screening and revision, and the paper was published in early April.

It was usually done in such a short period of time that it would take months or more, in fact, it had been prepared for years in advance. What’s more, it was possible because the research team had the latest next-generation sequencing equipment and had brought in excellent scientists. For almost eight years, the support of the Ministry of Science and Technology has been a strong foundation for the ibs research team to run for almost eight years. The infectious disease scandal will not end this time. We hope to be a ready Republic of Korea on a solid basic science.

*References
Kim et al., Cell, 2020. 181:1-8.
Sola et al., Annu. Rev. Virol., 2015. 2:265-88.
Fehr et al., Methods Mol. Biol., 2015. 1282:1-23.

※ Original source: Institute of Fundamental Sciences

The Institute of Fundamental Sciences (IBS) contains scientific knowledge and the latest research trends on coronavirus infection-19 (COVID-19≤Corona19) and sars-coronavirus-2 (SARS-CoV-2 or 2019-nCoV) cause of corona19. <코로나19 과학 리포트>publish. IBS scientists want to share with citizens the latest research trends and scientific issues, as well as research progress and ideas that will help prevent, diagnose, and treat new viruses.

https://www.ibs.re.kr/cop/bbs/BBSMSTR_000000000971/selectBoardArticle.do?nttId=18475&pageIndex=1&searchCnd=&searchWrd=

/ Kim Light-light, Director of RNA Research Group, Institute of Fundamental Sciences (IBS) And Professor, Faculty of Life Sciences, Seoul National University (RNA Biology)



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